TDK 32x writer "disappearing"

After rebooting, this drive is available for a while, but then the driver letter “disappears” from Windows Explorer and the writer can no longer be accessed. Any idea what might be going wrong?

Thanks!
Kevin

As a side note, I recently changed the motherboard from a Shuttle AK11 to an MSI KT7 Turbo 2 – the problem showed up on both.

Actuallly, come to thing of it, the problem may have started when I upgraded from a 20 Gb to 120 Gb hard drive.

Any thoughts?

–Kevin

Disappears??

What size power supply is in the box??

I am using a 300W power supply that came with my Antec SX830 case.